1. Field of the Invention
This invention pertains to a lightweight, compact apparatus, referred to as a deadend used to attach aerial fiber optic transmission lines or cables to support structures such as poles or towers.
2. Technology Review
Existing deadends are generally bulky and difficult to install. Several different types of deadend technology are presently used for joining aerial fiber optic cables to support structures. One type of deadend widely used is the formed wire deadend shown in FIG. 1. These deadends consist of bundles of wires joined side by side and formed into a helical ribbon. Three to four of these bundles are wrapped around the cable side by side to virtually surround the cable. A second layer of formed wires are wrapped over this inner layer. This second layer has a formed bail or attaching cable which is placed over a thimble clevis attached to the support structure.
The formed wire deadend is difficult to install. For example, wrapping the formed wires around the cable requires a great deal of hand strength. Also, the installer's fingers often get pinched while wrapping the formed wires around the cable. Further, these deadends can be as long as twelve feet and are heavy and bulky, and therefore, cannot be installed from the support structure. Also accurate alignment, which often takes a great amount of time, must be maintained between the bundles of formed wires.
A second type of deadend, shown in FIG. 2, is the split mesh Kellems.RTM. grip. These deadends operate like a Chinese finger grip to hold the cable. Woven wire mesh is wrapped around the cable and a wire or rod is used to weave the mesh edges together where they overlap to form a tubular woven wire mesh about the cable. As the cable load is transferred to the grip, the grip tightens along the cable.
Wrapping the woven wire mesh around the cable and weaving the edges together with the wire rod is somewhat awkward. Further, such weaving is time-consuming causing the split mesh Kellems.RTM. grip deadends to be somewhat costly to install.
A third type of deadend currently used is the conical type deadend. These deadends, as shown in FIG. 3, are typically used on smaller optical cables subject to low cable tension. Conical type deadends have a two piece frame with a conical slot that is assembled over the cable, and an attaching cable which is used to attach the frame to the support structure. Inserts which have an outside conical taper and an inside slot sized to grip the cable are placed over the cable and slide into the matching conical slot of the frame. As the pulling force on the cable increases, the inserts slide forward in the frame and tighten around the cable to prevent it from slipping. Problems of the conical type deadends include the difficulty of manufacturing the internal and external slots when the deadend is to be used with high load cables. Further, this type of deadend is difficult to install because the installation process includes assembly of the frame around the cable which requires additional labor and special tools.
Another type of deadend, as shown in FIG. 4, is the leverage or pivoting clamp deadend. Leverage deadends have one or more pivot points. Gripping plates on one side of the pivot and pulling points on the other function similar to pliers to grip the cable tighter as the cable tension increases. This type of deadend is typically used as a temporary cable grip during cable installation due to its small size and quick installation. However, this type of deadend is not recommended for permanent use because it is quite heavy and is expensive to manufacture. Further, the long-term performance of the leverage deadend is questionable, especially when subject to oscillating loads due to cable low frequency galloping. Galloping is a large amplitude cable oscillation caused by wind and resulting in loading and unloading of the deadend.
Bolted deadends, as shown in FIG. 5, are another type of deadend currently used. These deadends consist of a base plate with a groove sized to fit a specified cable design. A series of plates with matching grooves are bolted onto the top of the base plate with the cable sandwiched between. Bolted deadends are typically used for large cables and cables carrying very high cable loads. Again, this type of deadend is very heavy. Further, because of the numerous bolts that must be tightened, the bolted deadend is time-consuming to install.
Therefore there is a need for a deadend which is compact, lightweight and inexpensive to manufacture. Also needed is a deadend which is easy to install that meets the system performance requirements of strength and long term reliability without deteriorating cable performance and can be installed from the support structure.
It is an object of the present invention to provide a deadend for joining aerial fiber optic transmission lines or cables to support structures that is inexpensive and easy to install.
It is another object of the present invention to provide a deadend for joining aerial fiber optic transmission lines or cables to support structures that is compact and lightweight.
It is a further object of the present invention to provide a deadend for joining aerial fiber optic transmission lines or cables to support structures that is inexpensive to manufacture.
It is yet another object of the present invention to provide a deadend for joining aerial fiber optic transmission lines or cables to support structures that does not require special tools for installation.
It is still another object of the present invention to provide a deadend for joining aerial fiber optic transmission lines or cables to support structures that meets the system performance requirements of strength and long term reliability without deteriorating cable performance.
Additional objects and advantages of the invention will be set forth in the description that follows.